DIN is an abbreviation for Deutsches Institut für Normung, or German Institute for Standardization, which is a German manufacturing industry standards group. DIN connectors are round, with pins arranged in a circular pattern. This type of connector was used widely for PC keyboards, MIDI instruments, and other specialized equipment. Another type of DIN connector is the mini-DIN. As the name suggests, mini-DIN connectors are smaller in size than a regular DIN. They are still round, but with the pins arranged in horizontal rows rather than in a circular pattern. Mini-DIN connectors are used for S-video connections, PS/2 mouse & keyboards, and some other applications. DIN and mini-DIN connectors are both held in place by the friction of the connector body and by pins.
The 5-pin Din connector has 5 pins that are arranged in a circular pattern. This type of connector was commonly used for older AT-style computer keyboards.
The 4-pin Mini Din connector is the proper name for what is commonly referenced as an S-Video connector. The connector has 4 pins arranged in 2 rows, as well as a keying block to make certain the plug cannot be inserted improperly. Even though the S-Video connector has 4 pins, it only carries two signals — luminance and chrominance. The Luminance is a black-and-white wide-bandwidth television signal. The Chrominance is the color information of the video. The other 2 pins are used for signal ground connections.
The 6-Pin Mini Din has 6 pins as well as a keying block. This interface was first used on the IBM® PS/2 personal computer. For this reason the connector is often called a PS/2 connector. This connector has become the industry standard for connecting keyboards and mice.
The 8-pin Mini Din features three rows of pins with three pins in each of the top two rows and two pins in the bottom row. This connection was commonly used with the serial interface on older Apple® computers. Nowadays, it can sometimes be found on portable video devices, and projectors.